1. Field of the Invention
The present invention relates to a controllable electrode device for intracorporeal stimulation of body tissue, particularly of the type suited for intracardial stimulation of a heart.
2. Description of the Prior Art
Electrode devices are generally known in the art for intracardial stimulation of heart which include an electrode cable containing an elongate, flexible conductor having an exterior provided with a layer of insulation and an interior forming a channel which is capable of receiving an elongated member, such as stylet, for transmitting a pushing force to the distal end of the electrode, at which the electrode head is disposed. As used herein, "distal" means distal relative to a yet-to-be-connected stimulation device, or alternatively, that end of the electrode disposed at the treatment site.
In electrode devices of this type, it is of great importance for the electrode cable to be sufficiently pliant so that it is able, during advancement during implantation into a patient's heart via a vein, to follow the course of the vein without damaging the venous wall. In most instances, the electrode cable is introduced using a stylet, which is inserted into a channel inside the cable, and which is made of a material which achieves the desired stiffness necessary to advance the electrode cable in a vein. At difficult passages, for example, where the cable must bend sharply, the stylet is often retracted slightly, so that the distal end of the electrode cable displays maximum pliancy. After such a passage has been negotiated, the stylet is again advanced to the distal end of the electrode cable in order to push this end, for example, into the atrium or ventricle until the electrode head bears against the heart wall, for stimulation of the heart. When the electrode is in place, the stylet is withdrawn, which is a procedure that may damage the conductor, which often forms the channel for the stylet, at the locations of sharp bends in the vein in which the electrode cable has been inserted.
An electrode device of this type, having an electrode cable which is advanced in a vein with the aid of a stylet, is described, for example, in German OS 3 043 189.
Another electrode device of this type is described in the U.S. Pat. No 4,677,990. The stylet described therein is thinner at its anterior end than along the rest of the stylet, so the distal end of the cable can be bent into a J-shape.